1. Field of the Invention
The present invention relates, in general, to a washing machine equipped with a drying device to dry laundry and a method of controlling a drying process thereof.
2. Description of the Related Art
A washing machine equipped with a drying device is an apparatus that blows heated air into a space containing laundry to dry the laundry, and is designed to independently perform a drying operation, or to perform the drying operation in conjunction with general washing operations of the washing machine, that is, after a spin-drying process is complete.
Generally, the drying device is applied to drum-type washing machines.
When a drying process starts during an operation of the drum-type washing machine, a centrifugal fan operates and a drying heater turns on, so that hot air generated by the drying heater blows into a rotating tub of the drum-type washing machine. The laundry dries by repeating a process in which the laundry contained in the rotating tub rotates together with the rotating tub and then falls down to a bottom of the rotating tub. The hot air blown into the rotating tub is drawn to the centrifugal fan along a wall of a water tub, with moisture contained in the laundry being absorbed into the hot air. Thereafter, moisture, which is contained in the air circulated in the rotating tub and then drawn to the centrifugal fan, condenses on the wall of the water tub under an influence of a small amount of cold water that is supplied from a condensation hose connecting with an external water source to the wall of the water tub, and then the condensed moisture flows down to a bottom of the water tub. A small amount of condensed water collecting on the bottom of the water tub discharges from the washing machine through an outlet.
In a conventional method of controlling a drying process of the drum-type washing machine, a user may set a drying time for the laundry in consideration of a weight of the laundry. However, setting the drying time by the weight of the laundry is inaccurate and creates errors in the drying time setting. Further, since the moisture contained in laundry should be taken into consideration, even though the weight of a first laundry is a same as that of a second laundry, an amount of moisture in the first laundry may differ from that of the second laundry, thus, to accurately set the drying time is difficult.
In consideration of the above-described point, a method of controlling a dry process, in which a temperature of air blown into a rotating tub is detected and the drying process is terminated when the temperature of the air reaches a set temperature, is employed. However, although the method makes use of the temperature of the blown air, the drying time varies according to a weight of the laundry, moisture contained in the laundry and a temperature of the cold water supplied from an external water source, so that to accurately set the drying time is still difficult.
If the drying time for which the drying process is performed is to short, the drying process may be terminated before the laundry is completely dried, so that a drying performance may be lowered. In contrast, if the drying time is set to long, the laundry is excessively dried, so that the laundry rotated in the rotating tub may be damaged and, additionally, energy is wasted.